A shocking picture of physical, sexual and psychological violence being perpetrated against children on a daily basis has been revealed in a UN report.

The first UN study of global violence against children says such abuse is often socially approved or even legal.

It concludes that violence against under-18s occurs in every country, every society and every social group.

The UN has called on states to outlaw violence against children and to ensure their rights are protected.

The study, which was requested by UN Secretary General Kofi Annan, is the result of four years of research.

Psychological scars

The report's author, Professor Paulo Sergio Pinheiro, says the situation revealed is not acceptable and decades of silent abuse can no longer remain unchallenged.

"Protection from violence is a matter of urgency," writes Mr Pinheiro, "Children have suffered adult violence unseen and unheard for centuries."

The UN is calling on every country to have a national strategy to prevent violence against children.

The report, the first of its kind, charts various kinds of violence, from prostitution to school bullying, taking place in different stages and spheres of children's' lives - at home, in the community and in institutions.

It estimates that some 150 million girls, 14% of the planet's child population, are sexually abused each year, as well as seven percent of boys, or 73 million children.

Such violence can leave serious long-term psychological scars which result in increased risky sexual behaviour, substance abuse and violence towards others in adulthood.

Hidden violence

The study suggests that between 80-93% of children suffer physical punishment in their homes, although many of them do not speak of it due to stigma, shame and a lack of faith in legal systems.

The home can also be a dangerous place for some of the estimated 82 million girls who marry before the age of 18 and can face violence from their partners.

"There are several modalities of violence that are invisible or there is a wall of silence - violence inside the school, inside the home, at the workplace, the community and institutions," Mr Pinheiro told the BBC.

This is the moment to recognise children as being protected by rights, as full citizens

Gender also shapes the likelihood of experiencing different types of violence.

A study of 21 mainly developed countries, for example, found that up to 36% of women and 29% of men reported being sexually victimised during childhood.

But boys, especially in the 15-17 age group, are up to four times more likely to be murdered than girls of the same age.

The authors said they were encouraged by the participation of 135 governments from across the globe.

But the report recognises that one of the greatest challenges is changing a social mindset that tacitly accepts violence towards minors.

It includes a list of recommendations including the creation of national commissioners to prevent violence against children and national legal frameworks to protect children.

"After the emancipation of the workers in the 19th Century, the emancipation of the women in the 20th Century, I think that this is the moment to recognise children as being protected by rights, as full citizens, and not as mini-human beings or the property of their families," Mr Pinheiro said.